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Thread: Securing slab boxes

  1. #1
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    Securing slab boxes

    How do you guys secure your slab boxes so as to ensure they don't move during the concrete pour?

    Every meter or so I bind my conduit to the reinforcing mesh with wire but how do I get my slab box to sit solid against the shutter board to 1) ensure it doesn't move and 2) ensure no concrete flows between the box and shutter board?

    I got a big build coming up about 100 downlights 50 of them will be in slab.
    Want to do it properly so I don't sukkel down the line.

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    The last slab box job I did ... the boxes fitted between the block nice and tight ... you dont have to fill the box with paper but out of habit I just do it ... there is nothing worse than trying to fix problems once the slab is poured ... I add in a few extra pipes between the boxes ... just in case ... at 4s buck a meter ... compared to trying make a plan to get from one box to another ... no thanks

    drill the holes and fit the adaptors ... then take the paper from the cement bags and wet it properly ... pack it into the box nice and tight ... that prevent the box from filling up with cement.

    dont screw the boxes to the plywood otherwise you gonna have a problem when they try remove the shutter board.

    I carry rolls of 30m strapping with my GX 120 which I use to secure the pipes in the walls once we have finished chasing ... I secure the strap to the box them nail the strap to the board ... the boxes dont go anywhere.

    I also cut pieces about 300 mm long and secure them across all the couplings ... so that when they start pulling on the wire mesh they dont pull open the piping apart at the couplings.

    Make sure you are on site the day of the pour ... they give a rats ass about your conduit and boxes ... I have done a few commercial slabs and yet to have an issue with blocked or open pipes.
    Comments are based on opinion...not always facts....that's why people use an alias.

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    We have used 6inch nails and nailed through the box from the top into the shutter board so when the strip they nails can pull out without damage to the box. Bit difficult on steel shuttering
    We wrap the boxes with Buff Tape to stop concrete ingress

    Place the boxes before they start the steel work and then tube after bottom steel fix , before top steel.
    Ians points above with couplings are valid - keep the conduit off cuts and tie alongside the couplings to prevent them breaking

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    Thanks for replies

    These builders don't use rib and block by the looks of it instead they shutter the entire area and then do the pour.

    I like the idea of extra conduit between boxes as insurance.
    Was thinking of taking a conduit from last box in the circuit back to switch so I can enter circuit from both sides.

    About 60% of this house is 2way switching so IL have to link many of the switches together with conduit to get my strappers from the one to the other.

    Intermediate switching on staircase landing etc..
    Will have to put my thinking cap on for this.

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    The last project we did also got very complicated ... 3 days planning 2 hours installation ... way better than 2 hours installation and 10 days chasing chopping trying to make a plan.

    A tip ... fit a pipe between the box with the switch ... so from the switch to the box on both sides ... then fit a pipe directly from one "box" to the other "box" ... it will save you having to pull strap wires through all the boxes ... pick a colour and only use that colour for strap wires between the switches ... by the way there are much easier ways to do 2 way and intermediate switching ... and dont forget to to pull a neutral and earth tot he switch ... it cost a little more ... but you will thank me in the future ... the earth is handy for pulling in extra wires that might be needed later ... the neutral if the house gets smart.

    I am sure you do know the sunlight trick for conduit and wiring .. its the best lube .. specialy when you need 9 wires in a conduit.

    You can also use construction adhesive to secure you boxes to the shuttering ... another way to secure the box.

    rivet a short piece of ally angle iron inside the box to the side of the light ... drill a couple holes into it ... it is handy to hold the wires away from the light or if you need to secure a power supply up out of the way ... I had to fit power supplies for strip lights.

    Fit a few extra round boxes in the kitchen area where you think there might be under counter lights ... nothing worse than finishing a project then having to find way to drop cabling down to kitchen cupboard lights.

    Every single additional pipe we installed on the last project ended up being used for something ... we installed a lot of strip lights ... just on the outside steps alone we fitted 30 metres of strip light.
    Comments are based on opinion...not always facts....that's why people use an alias.

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    another tip ... get yourself some ends caps for the pipes ... Find it way better than using insulation tape.

    I know a GX 120 is expensive but if you have one ... man they make life easy when chasing and installing conduit ... no need for a drill and wall plugs ... I buy cheap black webbing ... shoot one nail into the webbing ... pull it over the conduit (no matter the size) and bang another nail on the other side ...and off to the next point ...

    In commercial building where we fit metal trunking (P8000 or 9000) cable tray or conduit or boxes (just not PVC boxes ... they smash into pieces ... same with PVC trunking) ...you just place the laser level ... and off you go bang bang its done ...no need for permits and all that crap for shooting blanks like the DX guns.
    Comments are based on opinion...not always facts....that's why people use an alias.

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    Ha I wish, I'm not at GX120 level yet.
    Only in my 4th month working for myself.
    Might have landed with my arse in butter though if this job goes well.But will see.

    Yeah client has requested I pull in extra neutral to each switch for future possible "smart" applications.

    I will use brown housewire for strappers and blue for extra neutral.
    I'm thinking of going 25mm pipe between switches.

    Give myself best chance of not sukkeling with fishtape.25mm bundle not cheap though.

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    Good luck and well done on your new adventure bud! Personally never done a slab but chased a couple for retro fits but if you can and keen to take some pics would love to see it

    But main reason for the message is that I believe if you using GP then the neutral has to be black. Only a multicore cable can be identified with tape etc but also I may be interpreting it wrong and that GP can be taped up. So any wiser gents or ladies have clarification on cable identification for GP ?

    SANS 10142-1:2020
    Edition 3
    135
    6.3.3.2 The means of identification for an a.c. circuit may be by colours or by
    numbers, as follows:
    a) where colours are used
    1) a neutral conductor shall be identified by black only,
    2) an earth continuity conductor shall be identified by the bi-colour
    green/yellow only, or by being bare. Green/yellow insulated conductors
    shall NOT be used as live conductors under any circumstances,
    3) a phase conductor shall be identified by a colour other than
    green/yellow, green or black, and
    NOTE Welding cable manufactured to SANS 1576 should not be used in
    circuits above 100 V.
    4) the colours may be applied at the ends of the conductor (of a multicore
    cable) by means of durable colour marking (e.g. insulating sleeves or
    by electrical insulating tape wound more than once around the
    conductor), and
    b) where numbers are used, “0” shall indicate the neutral conductor.
    NOTE Where the purpose or the function of a conductor is apparent, marking is
    not required.

    Sent from my SM-N960F using Tapatalk

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    Trying to source decent 4x4 switch modules ... is another challenge in SA ... rather fit more 4x2 flush boxes ... and make sure you sink them as deep as possible otherwise the smart switches dont sit flush then you have to 3 D print surrounds ... it works but not the best looking ... so make sure all the components are available before you start fitting the boxes ... I have a 19 mm this template which I use to make sure all the boxes are level and 20 mm deeper than the brick ... not he finished plaster.

    The template is a piece of 19 mm plywood cut 50x100 or 100x100 screwed to the box once they are packed with wet paper ... then a straight piece any length longer then 200 mm which I use to secure using the nail gun or wall plugs ... the box ready to be plastered into the wall ... I use a laser level to line up the tops screw so that every box in the building is exactly the same height and level even before it is plastered ... by doing this you will never have and issue with dimmers ... shelly devices ... or smart switches.

    I installed 2 x 25 mm and mounted the switches back to back then linked them interlinked them ... I also used double pole switch modules to keep it tidy .. CBI were the only 4x4 modules which could supply al the bell press and isolators.

    BEWARE of MCE 4x4 switch modules they are aware of the problem with the moulds ... and I am not sure that they plan to rectify the issue anytime soon ... considering I am the only person complaining the problem ... I have had to replace all the switches on the last

    MCE also have a problem with their shaver unit ... once again they are aware of the problem ... but as pointed out to me via email ... they sell R850 k worth of product a month and nobody else is complaining ... if you dont use a solid metal pin ... you have to pull the plug out half way to get it to make contact ...

    just be aware of these issues ... otherwise you gonna look like a real twat when the switches stick half way and you have to return to site to replace shaver units.
    Comments are based on opinion...not always facts....that's why people use an alias.

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    I agree with Dylboy ... use black wires for neutral ... not only because of the regs ... we use blue wires for the lighting returns.

    Another tip ... get yourself some white heat shrink to fit over the wire ... mark the circuit and point cut and fit to the end of the wire shrink slightly so that it has a snug fit ... it makes life so much easier when you start connecting or return to add stuff ... I use colour wires for light return wires ... but when you step up from building bashing low cost houses to more upmarket houses ... every little details helps with tracing stuff or fault finding.

    And make sketches of everything ... I buy those cheap brown soft covered book A4 college exercise books with quad and margin ... like 4 bucks at checkers ... the reason I do it ... because most of my customers stick around for many years ... if it is a hit and run job or you doing on a cut throat budget ... dont waste your time.
    Comments are based on opinion...not always facts....that's why people use an alias.

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